Understanding Stargardt’s Disease

Stargardt’s
Disease is form of macular dystrophy that begins early in life. Dr.
Stargardt first described this condition in 1909 giving it its name. It is
one of the most common forms of a juvenile macular degeneration.
Stargardt’s disease may occur in one of every 20,000 children over the age
6 and is usually diagnosed before the age of 20. Boys and girls are
equally affected by this condition. Over 25,000 Americans have Stargardt’s
disease.

Stargardt’s is usually a recessive inherited condition requiring the
person to receive a gene from each parent to cause the disease. However,
there have been a number of cases identified as dominant inheritance,
requiring only one gene from either parent. Recently researchers have
identified the gene, ABCR, now called abca4, which causes Stargardt’s
Disease. This brings hope that a treatment will eventually be available.

With
Stargardt’s Disease, the macula and surrounding retina are affected. The
macula is the very center of our retina. The images we see are focused on
the retina like the film in the camera. Unlike camera film where every
part of the film is equally sensitive, our retina concentrates the most
sensitive vision in the very center. Additionally, our best color vision
resides in the macula. Thus, damage to the macula results in loss of
visual acuity or sharpness of vision, decreased color vision and small
blind spots.

Diagnosis:
Early in the disease, the macula may appear normal which may slow the
initial diagnosis of Stargardt’s. Children may be misdiagnosed with a
psychological vision loss given as the diagnosis. In time, characteristic
changes occur in the retinas that help facilitate diagnosis. Fluorescein
angiography is a test in which a dye is injected into the arm and the flow
of this dye as it enters the eye is studied. The damaged retina sits above
a layer called the choroids which is rich in blood vessels that supply
nutrients to the retina. During angiography in a patient with Stargardt’s,
the damage to the retina blocks the flow of light from the choroids
causing a “dark choroid” and this may be used to help diagnosis. This test
alone is not considered to be completely diagnostic of the disease.

In
later stages of Stargardt’s Disease, the classic appearance of the retina
allows a much easier diagnosis. The appearance of a “beaten metal” macula
combined with small yellowish-white flecks (fundus flavimaculatus) in the
peripheral retina is typical of Stargardt’s disease.

Emotional Impact: Adolescent years are difficult for every child, but imagine
suddenly learning that your vision is failing. The sudden awareness to the
child and parents that the child is losing vision can be a devastating.
The family and the child need to learn immediately about low vision care.
Knowledge of the options to help the child can help the family and child
put the problem in perspective. Counseling may be needed to help the child
through their fears. Support groups or interaction between the parents of
other Stargardt’s patients can be beneficial.

Decrease of Visual Acuity:
Stargardt’s disease may first be detected by a mild loss of visual acuity
or sharpness of vision.In the early stages, however, the
vision may be near normal.Visual acuity measurements may also vary
duetothe effects of light exposure and one should not be
alarmed if your visual acuity varies on each test. Most Stargardt’s
patients have visual acuities from 20/100 to 20/400.One study of
Stargardt’s patients found that all persons tested had decreased visual
acuities of at least 20/200 within approximately nine years after onset.

Come
and Go Vision: As
Stargardt’s disease progresses, patients may experience small areas of
vision loss or blind spots. As images fall upon the damaged areas of the
retina, objects may disappear and reappear causing a come and go effect.

Eccentric Viewing:
Stargardt’s disease creates central blindspots that increase in size as
the disease progresses.Patients learn to turn their eyes in a
specific direction to see around the blindspots. They must place the image
on an area adjacent the macula. Family members and teachers need to
understand that this is an adaptive step used to maximize their vision.

Photostress and Dark Adaptation:
Children with Stargardt’s disease often complain of difficulty adapting to
the dark after sunlight exposure. Light striking our retina causes
chemical reactions to occur in the rods and the cones. Our retina must
continuously create new photo-reactive chemicals and remove the waste
products of these chemical reactions. When a Stargardt’s patient is
exposed to bright sunlight, the retina may become bleached by the light
and the sharpness of vision may decrease and blind spots may become
denser. These are temporary conditions, but can be prevented or lessened
by use of sun filters and hats.

From
laboratory studies in mice, it has been suggested that sunfilters may
lessen the formation of lipofuscin, which is the waste products of the
rods and cones. Lipofuscin, if allowed to accumulate, may damage the
retina. Mice, without the ABCR gene like patients with Stargardt’s, do not
accumulate these waste products when raised in darkness. Additionally,
younger patients, under 26 years old, transmit more ultraviolet light to
the retina due to the clarity of the crystalline lens which in theory may
lead to more retinal damage in Stargardt’s patients. More research is
needed.

Photophobia: The
damage to the retina also leads to greater internal reflection of light
often causing an increase in light sensitivity.

Color
Vision: Though new theories
indicate the damage may begin in rod cells, our black and white vision,
surrounding the macula, the condition eventually damages the macular area
where cone or color vision cells are. Color vision declines as the disease
progresses, but patients usually maintain a significant amount of color
vision.

The Paradox ofPeripheral Vision Sensitivity: Patient may miss or see
poorly objects that fall in their central vision, but the far peripheral
vision remains intact with Stargardt’s. It is not uncommon not be able to
see a face, but notice a piece of lint on the shoulder. Family members often mistake this ability as an indication
that the patient can see better than he or she claims.

Phantom Vision / Charles Bonnet Syndrome:
In more severe stages of vision loss, patients may experience Phantom
vision or visual hallucinations. These episodes are not usually related to
underlying psychiatric problems, but rather are normal attempt by the
brain to make sense of impaired sensory information. The brain may
embellish the image making it very real just as it does in our dreams.

Depth
Perception:
Depth perception is dependent on two good eyes. Anything that decreases
vision in one or both eyes will cause an immediate drop in our depth
perception.

The
Good News:
Stargardt’s never causes total vision loss. Peripheral vision is left
intact. Central vision is usually in the range of 20/100 to 20/400 with
younger patients usually showing less loss. Low vision care can help
Stargardt’s patients lead very normal lives. Following diagnosis every
Stargardt’s patient should have a low vision examination by a doctor
skilled in low vision rehabilitation.

Low
Vision Care:
Stargardt’s patients respond well to magnification. Simple bifocals may be
used in the early stages. In later stages, CCTV systems are helpful. It is
important to maintain good cosmetic appearance for young patients.
Mobility is usually minimally affected. Some Stargardt’s patients can
become bioptic drivers, but it may be for a limited time.

School
Age
Issues

In
children and teens with Stargardt’s disease, it is very important to have
adequate low vision care. These students may have light and glare control
problems in their classrooms. Adaptations including sitting away from the
window or shutting the curtains may be necessary. Also, these students
should be allowed to wear special sunfilters when needed to decrease glare
and light sensitivity.

Large
print materials may be indicated for these children. This may include
textbooks, worksheets, and tests. Due to their vision loss and difficulty
reading, some students may require extended time on tests and quizzes.

Because the vision loss may progress over time, each student should have a
Teacher of the Visually Impaired. A VI teacher will access the classroom
and educational plan for the child. With the low vision specialist’s
recommendations, the VI teacher makes adaptations including low vision
devices, large print materials and other special services the child will
need each year in school.

Because of the vision loss, there are also safety issues to look at in
young active students. Eyewear with polycarbonate lenses should be worn
for protection of the eyes from unexpected injury. Counseling should
include safety issues in physical education. Sports like swimming and
track are good options. Sports with fast moving projectiles may put young
Stargardt’s patients at risk. Protective face shields are essential if the
patient is to play in such a sport. With the proper safety devices,
patients have played hockey successfully.

Good
Advise from a Stargardt’s Patient:

“Don’t listen to negative influences.
Believe in yourself, and show others what you can do. Only “you” can find
your potential.”

Marla
Runyan, US Olympian and Stargardt’s patient and the first legally blind
athlete to compete in the Olympics

Gene Discovered for Stargardt Disorder A team of researchers from four institutions has
identified the gene that causes Stargardt. This disorder effects about 25,000 Americans
and is a progressive disorder of the retina. More precisely, Stargardt attacks the macula
which is responsible for central vision.